Multi-zone refrigeration system and apparatus



Jan. 4, 1966 E. A. GAMACHE 3,

MULTI-ZONE REFRIGERATION SYSTEM AND APPARATUS Filed May 5, 1964 3Sheets-Sheet 1 TO "N LGADER ERNEST A.GAMACHE BY T Jan. 4, 1966 E. A.GAMACHE 3,226,949

MULTI-ZONE REFRIGERATION SYSTEM AND APPARATUS 3 Sheets-Sheet 2 Filed May5. 1964 ERNEST A. GAMACHE BY $6M 14 5% Jan. 4, 1966 E. A. GAMACHE3,226,949

MUL'II-ZONE REFRIGERATION SYSTEM AND APPARATUS Filed May 5, 1964 3Sheets-Sheet 5 ERNEST A. GAMACHE IN VEN TOR.

FIG.3 M

United States Patent Ofifice Fatented Jan. 4, 1966 3,226,949 MULTI-ZONEREFRIGERATION SYSTlElt I AND APPARATUS Ernest A. Gama-she, WestCaldwell, N31, assignor to Worthington Corporation, Harrison, N .1, acorporation of Delaware Filed May 5, 1964, Ser. No. 364,925 6 Claims.(Cl. 6251t)) This invention relates to a refrigeration system operableto simultaneously service a plurality of cooling zones, exhibitingwidely varying temperatures. It relates in particular to a multi-stagecompressor adapted to provide hot compressed refrigerant to said system.

In a normal commercial refrigeration system, a refri erant is circulatedin liquid and vaporized phases through elements making up the system. Atthe system evaporator outlet, refrigerant gas at a predeterminedpressure is directed to the compressor suction inlet for recirculation.

In the instance of a multi-zone installation where cooling zones aremaintained at widely divergent temperatures one from the other,returning refrigerant gas streams will exhibit a comparable divergentpressure differential. For example, in a supermarket or similarinstallation handling food stuffs, at least one refrigerated section maybe required to operate at a temperature of about F. Other sectionsholding foods in cold storage, may require a constant temperature of aslow as minus 40 F. depending on the character of the food being store Itis known to be economically inefficient to equalize the pressure ofrefrigerant gas streams returning to a single compressor fromevaporating zones operating at divergent pressures. To accommodate suchconditions it is customary to employ separate compressors, orcompressors connected in tandem to receive refrigerant gas at a singlelow pressure, and to discharge the same as a hot stream at a higherpressure.

The present invention provides an improved, closed multi-zonerefrigeration system of the type contemplated in which at least twodifferent temperature cooling zones are simultaneously maintained. Amulti-stage compressor incorporated into the system feeds hot compressedgas to a condenser, said compressor being adapted to receive streams ofrefrigerant gas at pressures substantially equal to the pressures of thesystems respective evaporators. A first compressor stage receives avaporous stream from the low temperature and pressure zone forcompressing the same to an intermediate pressure. A higher secondcompression stage receives hot, partially compressed gas,

together with a second stream of refrigerant gas from the higherpressure evaporators. The second stream mixes with and cools the firststage discharge gas and also supplements the gas feed to the secondstage.

Unloader means cooperative with the respective compressor stages serveto adjust the capacity of each stage in accordance with the loadingconditions at the respective cooling zones. Also provided in thecompressor is means for introducing liquid refrigerant from the systemdirectly into the compressor intermediate stage, supplementing andcooling the second refrigerant stream as required.

It is therefore, an object of the invention to provide a refrigerationsystem having a plurality of evaporator units adapted to pass streams ofrefrigerant at varying pressures to provide varying degrees of coolingat different cooling zones.

Another object is to provide a refrigeration system operable at aplurality of pressure levels and having a refrigerant compressorapplicable in the system.

A still further object is to provide a refrigeration systemsimultaneously operable at a plurality of cooling levels and deliveringvaporized refrigerant streams at a first pressure and at a second higherpressure, said sy tem including a single multi-stage compressor forreceiving vaporized refrigerant at these varying pressures forcompressing the same.

Still another object is to provide a multi-stage compressor having aplurality of inlet means being maintained at different refrigerantpressures.

Another object is to provide a reciprocating compressor adapted formulti-stage operation, in a refrigeration system, and including a firststage operable at a low pressure, and being communicated with a secondstage operable at higher pressure, each of said stages being furnishedwith separate flows of refrigerant drawn from the system.

Another object of the invention is to provide a multistage compressorembodying interconnected first and second stages having substantiallyequal volumetric capacity, said first stage discharging into anintermediate chamber adapted to receive another stream of vaporizedrefrigerant to mix with vapors passing from the first low pressurestages to said second stage.

These and other objects of the invention will become clear to thoseskilled in the art from the following description of both the system andthe apparatus, made in conjunction with the appended drawings.

FIGURE 1 illustrates schematically a refrigerant system and unloadercircuit including a plurality of evaporators operable at differentpressure levels to provide cooling zones of divergent temperatures.

FIGURE 2 is a side elevation in partial cross section of a multi-stagecompressor adapted for use in the system shown in FIGURE 1.

FIGURE 3 is a segmentary view of a portion of the top of the compressorshown in FIGURE 2 with a portion of the wall broken away to showinternal structure.

FIGURE 4 is a segmentary view partially in cross section talten alongline 4-4 of FIGURE 3.

FIGURE 1 depicts schematically a refrigeration system of the typepresently contemplated which includes a common condenser and a pluralityof evaporators operable at different pressures and temperatures. Whilethe figure illustrates two evaporators, it is understood that addedunits may be employed in the system and be so connected to operateinbanks or other suitable arrangements of pressures and temperatures.The closed system includes a compressor of the multi-stage type having afirst compression stage connected to an intermediate chamber serving assuction for a second compression stage. Thus, a plurality of inletopenings communicated with the first stage form the intermediate chamberwhereby the compressor may be simultaneously fed at least two streams ofrefrigerant passed thereto from the respective evaporators.

The discharge side of the high compression stage is communicated withthe inlet of the condenser, after which refrigerant is passed in anormal manner to a receiver and through an expansion means communicatedwith the inlet side of the evaporators, thus forming the closed system.

Referring to FIGURE 1, the system shown diagrammatically includes areciprocating compressor 10 having a first low pressure stage 11connected to a higher pressure stage 12 through an intermediate chamber13. Discharge outlet 14 communicates through line 16 to the inlet ofcondenser 17. The downstream side of condenser 17 is connected throughline 18 to a liquid receiver 19 holding a supply of liquid refrigerantat condenser pressure. A first evaporator unit 21 is positioned in acooling zone to operate at a higher temperature of approximately 15 F. Asecond evaporator 22 is positioned in a second cooling zone and adaptedto operate at a lower temperature of approximately minus 40 F.

It should be appreciated that the temperatures and pressures hereinafterreferred to are designated for the purpose of facilitating thedescription of the invention. However, such temperatures will beadequate to supply cooling at relatively different cooling levels.

In accordance with conventional practice, the liquid holding portion ofreceiver 19 is communicated through expansion valve 23 to the upstreamor inlet side of evaporator 21. A second expansion valve 24 likewisecommunicates the liquid holding portion of receiver 19 to the inlet ofevaporator 22.

A return line 26 connected to the downstream side of evaporator 21carries vaporized refrigerant from the high pressure cooling zone toinlet 28 for directing refrigerant to intermediate chamber 13.Similarly, line 31 connected to the downstream side of evaporator 22conducts a second returning stream of vaporized refrigerant fromevaporator 22 to suction inlet 32, feeding the low pressure first stage.

The closed system may circulate a refrigerant such as R-IZ or R-22, ormixtures thereof. To facilitate the following description, it ispresumed that the refrigerating medium is R-22. At required coolingconditions, the low pressure evaporator 22 is controlled to operate at atemperature of approximately minus 40 F., and the high pressureevaporator 21 functions at a temperature of approximately 15 F.

The system, and the operating temperatures herein designated, exemplifyrequirements of a refrigeration installation adapted to provide thenecessary cooling to a multi-zone installation such as a supermarket orfood processing plant. In the instance of the latter, meat or otherperishable commodities are normally stored at a sufficiently lowtemperature to avoid deterioration of the product over a period of time.Thus, a low temperature of minus 40 F. is deemed adequate formaintaining the quality and condition of the frozen food. Evaporator 21is disposed in a section of the installation where a higher temperatureis required. This temperature can be approximately 15 E, which is normalfor a cutting or wrapping room where the product is only temporarilystored and sufficiently cooled to permit handling.

After initial compression in the first stage, refrigerant at anintermediate pressure and at a compressive temperature of approximately157 F. is delivered to intermediate chamber 13. It should be noted thataccording to the invention, the intermediate chamber is essentially aconnection or communicating passage from the discharge of the lowpressure stage to the suction of the high pressure stage.

Inlet 28 to intermediate chamber 13 receives vaporous refrigerant fromevaporator 21 at a temperature of approximately 15 F. Mixing of thesecondary or side load of refrigerant gas passed to the intermediatechamber 13 with partially compressed refrigerant from the first stage11, achieves two effects. First, it cools hot compressed refrigerantpassing from the first stage. Secondly, it supplements the flow ofrefrigerant to the second stage in sufficient amount to permit thevolumetric displacement of both first and second stages to besubstantially equal.

At the compressor discharge 14, hot refrigerant is delivered to air orwater cooled condenser 17, which is pre-set and controlled to operate ata temperature of approximately 105 F.

Description of the compressor Referring to FIGURE 2, a reciprocatingcompressor of the type presently contemplated includes a plurality ofcompression cylinders mounted within a casing, and operably connected toa single crankshaft. While the following description will be drawn tothe shown construction of a compression machine, it is appreciated thatpreferably the number of cylinders actually required can be any evennumber, each being of substantially equal volumetric capacity such thatthe first and second compression stages contain equal numbers ofpistons.

As shown in FIGURE 3, the respective compressor cylinders are numbered41 through 48 inclusive. Cylinders 42, 43, 46 and 47 constitute thefirst low pressure stage. Cylinders 41, 44, 45 and 48 comprise thehigher pressure stage. The cylinders comprising the respective high andlow pressure stages are physically separated and are radially mounted inbanks within the compressor casing 51.

Referring to FIGURE 2, compressor 10 includes a casing or shaped housing51 having opposed end openings. A wall 55 at one end of housing 51includes a recess, positioning a main shaft bearing 98. End bell 15 isremovably fastened to the casing opposite opening by bolts 94 positionedin flange 95, thereby forming a sealed enclosure to crankcase 52.

End bell 15 includes a center hub 96 extending into crankcase 52 forminga fluid tight seal at panel 97. Hub 96 positions a second main bearing99 disposed in alignment with bearing 98.

Crankcase 50 is rotatably disposed in crankcase 52 and journaled in mainbearings 98 and 99, having a keyed portion of the shaft extendingthrough the end bell 15 to engage a suitable drive member. A centralrecess in end bell 15, together with cover plate 75, defines a chamberabout crankshaft 50.

Crankshaft 50 includes a plurality of spaced throws, two being hereshown for engaging the lower end of piston rods associated with therespective compression cylinders.

Referring to FIGURES 2 and 4, casing 51 includes means forming apartition 54 which separates crankcase 52 from intake and dischargeportion of the respective high and low pressure stages.

Assembly 42 is illustrative of the remaining cylinders and includes apiston 56 pinned to rod 57, the latter being journaled to throw ofcrankshaft 52. A cylinder liner assembly 42 is positioned in housing 51,and partition 54, respectively, and fastened thereto by a plurality ofbolts 58. Low stage 57' extends downwardly into crankcase 52, beingsealably received at an opening formed in partition 54, by a seal ringor gasket 59.

Referring to FIGURES 3 and 4, partitions 61 and 62 extend longitudinallyof compressor casing, defining low pressure stage 11 and high pressurestages 12 and 12.

End bell 15 carried on casing 51 includes a low pressure suction inlet32 connected through means forming a passage, in communication with thelow pressure stage 11, for delivering vaporized refrigerant to cylinderassemblies 42, 46, 43 and 47.

As seen in FIGURE 2, each compression cylinder is provided withconcentric ring type suction and discharge valves for controlling flowof gas to and from the cylinder.

Casing 64 fastened to the upper surface of housing 51 forms a dischargemanifold 64' for cylinders 42 and 46. Passage means 67 in the upper wallof casing 52, directs refrigerant leaving the low pressure stage 11 intothe intermediate chamber 63.

Referring again to FIGURE 2., the annular valve arrangement includesrefrigerant forming a passage 69 communicated with suction passage 63for introducing refrigerant to the cylinder assembly 42. The valve meansincludes the annular member 71 having a channel 72 formed therein andcommunicated with passage 69. A movable element 73 is normally urged bysprings '74 to close passage 69. Annular protruding lip 76 positionedadjacent element 73, limits upward movement of the latter when piston 56is on the intake stroke thereby drawing refrigerant through passage 69and into the cylinder liner.

Cap 77 forms a head member to the cylinder liner assembly and includes aperipheral groove 78 in communication with the discharge opening 79 fordirecting compressed refrigerant gas from the first stage, into thefirst stage manifold 64'. A diaphragm 81 retained in groove 78 is biasedto regulate discharge of refrigerant.

On the upstroke of piston 56, diaphragm 81 is displaced against spring82 a predetermined pressure thereby discharging hot refrigerant gas atfirst stage pressure.

Referring to FIGURE 3, hot refrigerant gas flows from the first lowpressure stage into intermediate chamber 68, and is re-distributedtherefrom to compartments 12 and 12 making up high pressure stages, bothof which compartments are disposed outboard of the low pressure stages.Passageways 83 and 84 are communicated with the high pressure stages 12and 12 holding compression cylinder 41, 45, 44 and 48.

A shown in FIGURE 4, second stage inlet chambers 36 and 86' arecommunicated through restrictive passage means 37 to crankcase 52, toeffect the proper pressure balance across the high stage pistons bybleeding vapor from the high stage suction to the crankcase.

Referring to FIGURE 2, means forming a second suction inlet 87 is formedin housing 51 providing communi cation with intermediate chamber 68.Suction opening 87 is provided with a suitable connection receiving aline connected to the downstream side of evaporator 21 Wherebyrefrigerant gas may be introduced into intermediate chamber 68 formixing with hot compressed refrigerant discharged from the firstcompression stage 11.

tion and arrangement to the valve means regulating flow to and from thelow pressure cylinder. As shown in FIG- URE 4, the high pressurecylinders discharge hot compressed refrigerant into discharge manifold88 formed by casing 89, suitably carried in place on casing 51 by bolts91. A passage means 92 formed in casing d9 carries refrigerant atdischarge temperature and pressure through discharge opening 14 forpassage to condenser 17.

Unloader arrangement Referring to FIGURE 2, low pressure cylinder 46 isshown provided with a shut off means for unloading certain cylinders,thereby varying the capacity of the compressor. Although the unloaderdevice is shown only in respect to cylinder 46, it is understood thatone or more of the remaining low compression cylinders and one or moreof the high pressure cylinders, may similarly be provided with unloadingmeans communicated with a central control for regulating the respectiveunloading units.

.Unloader assembly 1% is shown in FIGURE 2, and includes annular ring104 carried on the outer Wall of liner 101 and sealably fastened theretoas a permanent peripheral seal or by means of resilient O-rings. Anozzle 102 is threadably carried in partition 54 and connected throughconduit 103 to a source of oil or other pressurizing medium foractuating the unloader. Nozzle 102 is held in a substantially uprightposition and includes a central opening extending therethroughcommunicating with conduit 103. A ring member 104 includes an innersealing surface having a ring 106 disposed in rubbing contact with theouter wall of liner 57 conforming a fluid type seal therewith. A cavityformed in the upper face of ring member 104 defines an annular openingdisposed her and disposed in contact with the adjacent wall. Upper face111 of the ring member is adapted to engage the lower surface of Valvering 112 having passages 69 disposed therein. The lower face of ring 104is provided with a plurality of bores 114 adapted to receive and holdsprings 116 for normally biasing ring 104 upward into engagement withthe lower surface of ring valve 112.

Referring to FIGURE 1, a compressor unloading system adapted to theinstant invention incorporates a pressurizing source including a pumphaving a suction inlet communicated With an oil reservoir 117. Solenoidvalve means 12% is connected in line 119 to pump 115 discharge forregulating the flow of pressurized oil to the respective nozzles 102 atthe individual unloaders.

Referring to FIGURE 1, following a normal unloading system, valve 120 isrepresentative of similar valve arrangements connected to remaining highor low pressure cylinders.

In the unloaded position, oil is redirected from the unloader assemblyat compressor cylinder 46 to the oil reservoir, thereby reducing the oilpressures permitting the latter to be spring biased to the cut offposition, blocking the flow to said cylinder. Thus, when one or morecylinders in the first stages are to be unloaded, removal of pressurefrom conduit 103 will permit springs 116 to urge the valve ring member113 upwardly to engagement at the lower surface of valve ring 112.

When the load on the system requires that a cooling capacity be reduced,unloading is achieved by cutting off flow of gas from suction chamber 63to passage 6%. In like manner, each of the unloading assemblies mayserve to reduce the volumetric capacity of either or both the first andsecond compression stages.

As seen in FIGURE 1, individual cylinder unloacler assemblies 100 areconnected to a control center 110. The control center is in turncommunicated by sensing means to evaporators 21 and 22 to receive asignal. The control means may be of a type known to the art and soprogrammed to establish a compressor capacity pattern in accordance witha predetermined load pattern.

Operation The preferred start-up procedure for the compressor followssubstantially the steps recommended for similar refrigerant systemcompressors. For example, to facilitate starting up, the compressioncylinders are at maximum unloaded condition to lessen the startingburden, and maintained thus until the compressor reaches rated speed.

For full or rated operation conditions, all cylinders are originallyloaded. Referring to FIGURE 1, a hypothetical load as heretofore noted,consists of evaporator 21 being operated at a high pressure to maintaina temperature of approximately 15 F. Evaporator Z2 is simultaneouslyoperable to maintain a temperature of approximately minus 40 F.Refrigerant vapor from the downream side of evaporator 21 is conductedthrough line 26 to inlet 28 of the compressor intermediate chamber.Simultaneously, gas from evaporator 22 is conducted by conduit 31 toinlet 32 of the first compressor stage. In the intermediate chamber 13,partially compressed refrigerant gas at a temperature of about F. fromthe first compression stage mixes with refrigerant gas received fromevaporator 21.

Thus, the total output of the first stage compressor cylinders issupplemented by a secondary flow of refrigerant from the high pressureportion of the system, the latter flow being hereinafter referred to asthe side load on the compressor.

Since both first and second compression stages may be of substantiallyequal volumetric displacement the side load injected into intermediatechamber 13 effects two functions. First, it serves to cool heated firststage discharge gas. Secondly, it provides the additional volume of gasflow to the second compression stage.

Partial loading At part load operation, return vapor flow from theevaporators to the compressor 10 may result from a reduction in thecooling load at either or both evaporators 21 and 22. When the vaporfeed to the first compression stage 11 is reduced, one or more cylindersin said stage may be unloaded and the output of the remaining loadedcylinders fed into the second compression stage.

Simultaneously, the volumetric displacement of high pressure cylindersis balanced to receive the intermediate stage discharge of partiallycompressed refrigerant gas. Thus, one or more cylinders in the highpressure second stage are unloaded to maintain the compressor dischargeconditions.

When the cooling load on high pressure evaporator 21 is reduced, theintermediate or normal side load to compressor 10 is reducedaccordingly. To supplement the side load to the cooling effect firstcompression stage discharge, regardless of the evaporator output, meansis provided for introducing liquid refrigerant directly into theintermediate chamber.

As shown in the schematic FIGURE 1, conduit 130 is connected to theliquid holding portion of condenser 17 or receiver 19. Valve means 131interposed in line is solenoid operated to adjust flow of liquid passingtherethrough. Thus, refrigerant on entering intermediate stage 13 isimmediately vaporized at the higher intermediate stage temperature toform a gaseous mixture for combining with the discharge from the firstcompression stage.

Unloader control Referring to FIGURE 1, evaporators 21 and 22 againoperate at a temperature of 15 F. and minus F., respectively. Line 31communicates the outlet of the evaporator 21 to the downstream side ofthe first compression stage. Similarly, line 24 communicates the outletof the higher pressure evaporator 21 to the inlet 32 communicated withthe intermediate stage of the compressor. As has been previouslydescribed, hot compressed refrigerant gas leaving the compressor at line16 is directed to the upstream side of condenser 17 at a temperature ofabout 215 F.

Valve means 131 is disposed in line 130 and includes a solenoid tocontrol passage of liquid therethrough. Temperature sensing means 110 ispositioned in line 16 immediately downstream of compressor discharge 14to monitor the temperature of hot compressed gaseous refrigerant passingto condenser 17. Thus, when the output of one or more of the evaporatorsdecreases thereby indicating a lesser temperature at the compressordownstream side, valve 131 will automatically open to meter a controlledflow of liquid refrigerant from the high pressure side of the system tothe compressor intermediate stage 13.

Conversely, in the event the discharge temperature of hot compressedrefrigerant at the compressor rises above the desired 2l6 F., valve 131is automatically responsive to the change, to throttle the rate of flowof liquid entering the intermediate stage from the liquid part of thesystem.

Sensing means 113 is normally disposed in the evaporator 21 liquidholding portion and may include an arrangement normally adapted for suchpurpose comprising a pressure sensitive liquid containing bulb disposedwithin the evaporator and being responsive to pressure changes therein.Similar sensing means 114 is disposed in evaporator 22 and performs alike function of monitoring the pressure therein.

From the foregoing it is seen that the presentation provides a novel andimproved compressor structure for use in a multi-zone refrigerationsystem not heretofore known. It is understood, however, that thedisclosed embodiment represents a preferred form of the device which mayhe modified and adjusted without departing 8. from the spirit and scopeof the invention as'defined in the appended claims.

What is claimed is:

1. A refrigeration system comprising:

(a) a compressor operatively connected to a source of motive power,

(b) a condenser receiving gaseous refrigerant from the compressor tocondense the same,

(c) a first evaporator receiving liquid refrigerant from the condenser,

(d) a second evaporator receiving liquid refrigerant from the condenserand operating at a temperature substantially higher than the operatingtemperature of the first evaporator,

(e) expansion means disposed between the condenser and each of theevaporators to expand the liquid refrigerant selectively responsive tothe operating temperature of the evaporators,

(f) The compressor having a first stage and a second stage,

(g) the first stage of the compressor connected to draw refrigerant fromthe first evaporator and compress the same,

(h) the second stage of the compressor connected to draw refrigerantfrom both the first stage and the second evaporator in a combined flowfor compressing the refrigerant prior to discharge thereof into thecondenser,

(i) a first unloader means operatively connected with the first stage ofthe compressor,

(j) a second unloader means operatively connected with the second stageof the compressor, and

(k) a control means to sense the operating temperature conditions of therefrigeration system and to selectively operate the first unloader meansand the second unloader means to maintain the volumetric displacement ofthe compressor responsive to the operating load conditions.

2. A refrigeration system comprising:

(a) a compressor operatively connected to a source of motive power,

(b) a condenser receiving gaseous refrigerant from the compressor tocondense the same,

(c) a first evaporator receiving liquid refrigerant from the condenser,

(d) a second evaporator receiving liquid refrigerant from the condenserand operating at a temperature substantially higher than the operatingtemperature of the first evaporator,

(e) expansion means disposed between the condenser and each of theevaporators to expand the liquid refrigerant selectively responsive tothe operating temperature of the evaporators,

(f) the compressor having a first stage and a second stage,

(g) the first stage of the compressor connected to draw refrigerant fromthe first evaporator and compress the same,

(h) the second stage of the compressor connected to draw refrigerantfrom both the first stage and the second evaporator in a combined flowfor compressing the refrigerant prior to discharge thereof into thecondenser, and

(i) the first st-ages discharge of refrigerant at a substantially highertemperature that the temperature of the refrigerant combining therewithfrom the second evaporator whereby the first stage flow is cooled andadded to so that the combined flow of the second stage is ofsubstantially the same volumetric displacement as that of the firststage.

3. A refrigeration system comprising:

(a) a compressor operatively connected to a source 'of motive power,

(b) a condenser receiving gasous refrigerant from the compressor tocondense the same,

(c) a first evaporator receiving liquid refrigerant from the condenser,

(d) a second evaporator receiving liquid refrigerant from the condenserand operating at a temperature substantially higher than the operatingtemperature of the first evaporator,

(e) expansion means disposed between the condenser and each of theevaporators to expand the liquid refrigerant selectively responsive tothe operating temperature of the evaporators,

(f) the compressor having a first stage and a second stage,

(g) the first stage of the compressor connected to draw refrigerant fromthe first evaporator and compress the same,

(h) the second stage of the compressor connected to draw refrigerantfrom both the first stage and the second evaporator in a combined flowfor compressing the refrigerant prior to discharge thereof into thecondenser,

(i) an intermediate chamber means disposed between the first stage andthe second stage,

(j) the first stage discharging its refrigerant into the intermediatechamber means, and

(k) the second evaporator discharging a predetermined quantity ofrefrigerant into the intermediate chamber means to cool and mix with therefrigerant from the first stage whereby the volumetric displacement ofthe second stage is substantially equal to that of the first stage.

4. The combination claimed in claim 3 wherein:

(a) the condenser discharging a predetermined quantity of liquidrefrigerant into the intermediate chamber wherein it will flash intogaseous refrigerant to supplement the flow of gaseous refrigerant fromthe second evaporator whenever the flow therefrom is below thepredetermined quantity required to build up the volumetric displacementof the second stage to a substantially equal amount to that of the firststage.

5. A refrigeration system comprising:

(a) a compressor operatively connected to a source of motive power,

(b) a condenser receiving gaseous refrigerant from the compressor tocondense the same,

(c) a first evaporator receiving liquid refrigerant from the condenser,

(d) a' second evaporator receiving liquid refrigerant from the condenserand operating at a temperature substantially higher than the operatingtemperature of the first evaporator,

(e) expansion means disposed between the condenser and each of theevaporators to expand the liquid refrigerant selectively responsive tothe operating temperature of the evaporators,

(f) the compressor having a first stage, a second stage and anintermediate chamber means connecting said first and second stages,

(g) the first stage of the compressor connected to draw refrigerant fromthe first evaporator,

(h) the first stage of the compressor to discharge the refrigerant intothe intermediate chamber means at a temperature much higher than thetemperature of the refrigerant in the second evaporator,

(i) the second evaporator to pass refrigerant into the intermediatechamber means at a pressure substantially equal to the pressure of therefrigerant from the first stage, and

(j) the second stage of the compressor to draw refrigerant from theintermediate chamber means including the combined flow of the firststage and the second evaporator for compressing the refrigerant prior toits discharge therefrom into the condenser.

6. A multi-stage compressor for use in a refrigeration system having atleast two evaporators, one of which op- 2 erates at a substantiallyhigher temperature and pressure than the other, the compressorcomprising:

(a) a casing having a plurality of chamber means formed therein,

(b) a first compression stage disposed in one of the chamber means andcommunicating with the evaporator of lower temperature and pressure,

(c) a second compression stage disposed in another of the chamber meansremote from the first compression stage,

((1) an intermediate chamber means communicating the first compressionstage and the second compression stage,

(e) the intermediate chamber means receiving gaseous refrigerant fromthe evaporator of higher temperature and pressure to increase thequantity of refrigerant flow thereof whereby the volumetric displacementof the second compression stage is substantially equal to that of thefirst compression stage.

References Cited by the Examiner UNITED STATES PATENTS 2,553,623 5/1951Zumbra 62-113 2,578,139 12/ 1951 Jones 62-510 2,585,908 2/1952 Backstrom62-510 X 2,765,976 10/1956 Stewart 230-182 2,888,809 6/ 1959 Rachfal 62510 X 2,956,738 10/1960 Rosenschold et al. 230-188 3,033,009 5/1962Berger et al. 62510 X 3,150,498 9/1964 Blake 62-81 FOREIGN PATENTS843,093 7/ 1952 Germany. 872,336 7/ 1961 Great Britain.

ROBERT A. OLEARY, Primary Examiner. LLOYD L. KING, Examiner.

1. A REFRIGERATION SYSTEM COMPRISING: (A) A COMPRESSOR OPERATIVELYCONNECTED TO A SOURCE OF MOTIVE POWER, (B) A CONDENSER RECEIVING GASEOUSREFRIGERANT FROM THE COMPRESSOR TO CONDENSE THE SAME, (C) A FIRSTEVAPORATOR RECEIVING LIQUID REFRIGERANT FROM THE CONDENSER, (D) A SECONDEVAPORATOR RECEIVING LIQUID REFRIGERANT FROM THE CONDENSER AND OPERATINGAT A TEMPERATURE SUBSTANTIALLY HIGHER THAN THE OPERATING TEMPERATURE OFTHE FIRST EVAPORATOR, (E) EXPANSION MEANS DISPOSED BETWEEN THE CONDENSERAND EACH OF THE EVAPORATORS TO EXPAND THE LIQUID REFRIGERANT SELECTIVELYRESPONSIVE TO THE OPERATING TEMPERATURE OF THE EVAPORATORS, (F) THECOMPRESSOR HAVING A FIRST STAGE AND A SECOND STAGE, (G) THE FIRST STAGEOF THE COMPRESSOR CONNECTED TO DRAW REFRIGERANT FROM THE FIRSTEVAPORATOR AND COMPRESS THE SAME, (H) THE SECOND STAGE OF THE COMPRESSORCONNECTED TO DRAW REFRIGERANT FROM BOTH THE FIRST STAGE AND THE SECONDEVAPORATOR IN A COMBINED FLOW FOR COMPRESSING THE REFRIGERANT PRIOR TODISCHARGE THREOF INTO THE CONDENSER, (I) A FIRST UNLOADER MEANSOPERATIVELY CONNECTED WITH THE FIRST STAGE OF THE COMPRESSOR, (J) ASECOND UNLOADER MEANS OPERATIVELY CONNECTED WITH THE SECOND STAGE OF THECOMPRESSOR, AND (K) A CONTROL MEANS TO SENSE THE OPERATING TEMPERATURECONDITIONS OF THE REFRIGERATION SYSTEM AND TO SELECTIVELY OPERATE THEFIRST UNLOADER MEANS AND THE SECOND UNLOADER MEANS TO MAINTAIN THEVOLUMETRIC DISPLACEMENT OF THE COMPRESSOR RESPONSIVE TO THE OPERATINGLOAD CONDITIONS.